In general, air admittance valves are used in plumbing systems as an alternative to vent systems that require venting through a complicated pipe system and/or rooftop vent system. Air admittance valves are one-way mechanical valves that may be located in a ventilated space to alleviate a need to connect to a central vertical vent (or to provide a separate vertical vent) that passes through the roof of a structure. FIG. 1 shows a typical application of an air admittance valve. Air admittance valves are normally closed, but open during a negative pressure condition, such as when wastewater is released. This allows air to enter the plumbing system and facilitate drainage. Once the flow of the wastewater ceases, the valve closes and remains closed until another negative pressure condition occurs. In such a manner, odors are prevented from escaping from the vent system.
Many air admittance valves rely on gravity to close the valve once a negative pressure condition ceases. Such air admittance valves usually include sealing members that are constructed of multiple components. Typically, a rigid plate or frame structure is used to carry a thin flexible sealing member to and from closed and open positions. In many instances the thin flexible sealing member is bonded, stretched across, or otherwise fixed to the rigid frame structure. An example of such a design is described in U.S. Pat. No. 4,535,807.
These multipart constructions, however, are difficult and expensive to manufacture. Additionally, any detachment of the sealing member from the rigid frame structure is likely to result in inferior, and in some situations, failed performance of the air admittance valve. Furthermore, in many situations the ability of the sealing member to perform the sealing function is dictated by the accuracy of the dimensions of the frame structure. For instance, frame structures that have certain discontinuities, uneven surfaces, or other dimensional aberrations may not allow the sealing members to seal the valve in the closed position.
There is a need, therefore, for an improved air admittance valve that is configured to vent pipe systems to the ambient environment. The improved air admittance valve should be simpler and less expensive to manufacture, and should also provide enhanced performance.